In optical, magneto-optical and magnetic disc drives used for data storage, an actuator arm positions read or write heads over the disc to acquire information from the disc or store information to the disc. Movement of the actuator arm is typically controlled by a magnetic motor that includes a conductive coil position between a magnetic assembly. Typically, the magnetic assembly consists of two magnetic pieces bonded to two respective backirons that are maintained a fixed distance apart so that the conductive coil can move between the magnets.
To ensure consistent and predictable actuator arm movement, each magnetic assembly must be constructed with extreme precision so that variations between magnetic assemblies are minimized. In particular, the magnets must be precisely positioned relative to their respective backirons so that the position of the conductive coil relative to the magnet is consistent in each disc drive.
This type of accuracy and consistency cannot be achieved without the use of bonding stations that clamp the backiron and the magnet in a desired spatial relationship during bonding.
Typically, bonding stations achieve the proper alignment between the magnetic assembly and the backiron by using a lateral actuator and a staggered back assembly. The lateral actuator carries a movable front assembly that engages the magnet and the backiron as it moves toward the staggered back assembly and thereby presses the magnet and the backiron toward the staggered back assembly.
The staggered surfaces of the back assembly produce the desired spatial relationship between the magnet and the backiron. In particular, the magnet and the backiron contact two separate surfaces on the back assembly. These two surfaces are staggered relative to one another such that the surface contacting the magnet is closer to the front assembly than the surface contacting the backiron.
The front assembly also includes two separate portions that individually contact the magnet and the backiron respectively. In particular a nylon pusher on the front assembly contacts and presses the magnet and two locating pins contact the backiron and force the backiron toward the back assembly.
In order to properly position the magnet on the backiron, it is important that the end of the nylon pusher that contacts the magnet is the proper lateral distance from the locating pins.
In prior art bonding stations, this distance is determined by measuring the distance between a surface of the front assembly facing away from the back assembly and a housing of the lateral actuator. The measurements are typically performed using "go" and "no-go" blocks. The "go" block must fit between the lateral actuator housing and the back surface of the front assembly while the "no-go" block must not fit in this space. To achieve the proper distance between the front assembly and the back assembly, the position of the front assembly on the lateral actuator arm was adjusted until the proper distance was achieved.
However, measuring the proper position for the front assembly based on the distance from the back surface of the front assembly to the housing of the actuator is undesirable since it does not directly measure the distance from the nylon pusher to the back assembly or the distance from the locating pins to the back assembly. By measuring the distance from the back surface of the front assembly to the actuator housing, the prior art does not take into account numerous tolerasce errors that occur because of variations in the size of the font assembly, and variations in the location of the actuator housing relative to the back assembly. As such, prior art calibration tools do not properly calibrate existing bonding stations.
The present invention provides a solution to this and other problems, and offers other advantages over the prior art.